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Title: MOJAVE. XII. ACCELERATION AND COLLIMATION OF BLAZAR JETS ON PARSEC SCALES

We report on the acceleration properties of 329 features in 95 blazar jets from the MOJAVE Very Long Baseline Array program. Nearly half the features and three-quarters of the jets show significant changes in speed and/or direction. In general, apparent speed changes are distinctly larger than changes in direction, indicating that changes in the Lorentz factors of jet features dominate the observed speed changes rather than bends along the line of sight. Observed accelerations tend to increase the speed of features near the jet base, ≲ 10-20 pc projected, and decrease their speed at longer distances. The range of apparent speeds at a fixed distance in an individual jet can span a factor of a few, indicating that shock properties and geometry may influence the apparent motions; however, we suggest that the broad trend of jet features increasing their speed near the origin is due to an overall acceleration of the jet flow out to deprojected distances of the order of 10{sup 2} pc, beyond which the flow begins to decelerate or remains nearly constant in speed. We estimate intrinsic rates of change of the Lorentz factors in the galaxy frame of the order of Γ-dot /Γ≃10{sup −3} to 10{supmore » –2} yr{sup –1}, which can lead to total Lorentz factor changes of a factor of a few on the length scales observed here. Finally, we also find evidence for jet collimation at projected distances of ≲ 10 pc in the form of the non-radial motion and bending accelerations that tend to better align features with the inner jet.« less
Authors:
 [1] ; ;  [2] ;  [3] ; ; ;  [4] ;  [5]
  1. Department of Physics, Denison University, Granville, OH 43023 (United States)
  2. Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907 (United States)
  3. Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow (Russian Federation)
  4. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)
  5. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
Publication Date:
OSTI Identifier:
22364616
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 798; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; BL LACERTAE OBJECTS; BLACK HOLES; DISTANCE; GALAXIES; JETS; ORIGIN; QUASARS; VELOCITY